All (n=2359) | Tobacco smoke exposure | p-value | ||
Yes (n=378) | No (n=1981) | |||
Survey cycle | 0.29 | |||
2005–2006 | 882 (24.6) | 156 (28.0) | 726 (24.0) | |
2007–2008 | 457 (24.5) | 67 (25.4) | 390 (24.3) | |
2009–2010 | 526 (22.7) | 88 (23.6) | 438 (22.5) | |
2011–2012 | 494 (28.3) | 67 (23.0) | 427 (29.3) | |
Age (years) | 15.5 (15.3–15.6) | 17.1 (16.8–17.3) | 15.2 (15.0–15.3) | <0.0001 |
BMI (z-score) | 0.62 (0.57–0.68) | 0.57 (0.41–0.73) | 0.63 (0.56–0.70) | 0.52 |
Sex | 0.001 | |||
Male | 1202 (51.4) | 240 (60.6) | 962 (49.6) | |
Female | 1157 (48.6) | 138 (39.4) | 1019 (50.4) | |
Race/ethnicity | 0.002 | |||
Non-Hispanic White | 641 (58.4) | 144 (67.3) | 497 (56.7) | |
Non-Hispanic Black | 684 (14.8) | 112 (13.8) | 572 (15.0) | |
Mexican American | 646 (13.5) | 70 (8.3) | 576 (14.6) | |
Other | 388 (13.2) | 52 (10.6) | 336 (13.7) | |
Family income to poverty ratio | 0.0004 | |||
0–1.0 | 734 (23.6) | 162 (34.9) | 572 (21.3) | |
1.1–3.0 | 859 (35.6) | 128 (37.8) | 731 (35.1) | |
>3.0 | 612 (40.9) | 70 (27.3) | 542 (43.6) | |
Leisure-time physical activity (h per week) | 0.07 | |||
<3 | 1032 (39.3) | 176 (46.7) | 856 (37.8) | |
3–7 | 539 (25.1) | 75 (21.6) | 464 (25.8) | |
>7 | 778 (35.6) | 124 (31.7) | 654 (36.4) | |
Current allergic conditions | 0.34 | |||
Yes | 630 (27.3) | 28 (8.5) | 171 (10.4) | |
No | 1729 (72.7) | 350 (91.5) | 1810 (89.6) | |
Examination session | 0.71 | |||
Morning | 1174 (50.3) | 194 (51.3) | 980 (50.1) | |
Afternoon | 777 (31.7) | 124 (33.0) | 653 (31.5) | |
Evening | 408 (18.0) | 60 (15.6) | 348 (18.4) | |
Time interval since last shower/bath (h) | 0.11 | |||
≤2 | 312 (14.2) | 56 (16.3) | 256 (13.8) | |
3–6 | 578 (23.2) | 102 (24.9) | 476 (22.9) | |
7–14 | 584 (25.0) | 105 (28.2) | 479 (24.3) | |
>14 | 885 (37.6) | 115 (30.6) | 770 (39.0) | |
Sampling season | 0.09 | |||
November–April | 1222 (42.8) | 176 (37.8) | 1046 (43.8) | |
May–October | 1137 (57.2) | 202 (62.2) | 935 (56.2) | |
Swimming pool/hot tub/steam room use within 72 h | 0.02 | |||
Yes | 131 (8.9) | 15 (5.1) | 116 (9.7) | |
No | 2228 (91.1) | 363 (94.9) | 1865 (90.3) | |
Family history of asthma | 0.48 | |||
Yes | 455 (22.3) | 80 (24.1) | 375 (21.9) | |
No | 1904 (77.7) | 298 (75.9) | 1606 (78.1) | |
Ever (lifetime) asthma | 0.11 | |||
Yes | 441 (20.4) | 93 (24.6) | 348 (19.6) | |
Never | 1918 (79.6) | 285 (75.4) | 1633 (80.4) | |
Current asthma | 0.26 | |||
Yes | 196 (9.1) | 45 (11.0) | 151 (8.7) | |
No | 2163 (90.9) | 333 (89.0) | 1830 (91.3) |
Data are presented as n (%) or mean (95% CI), unless otherwise stated; accounting for complex, multistage sampling survey designs (e.g. sampling weights, stratification and clusters) to ensure nationally representative estimation. 31, 154 and 10 participants had missing information on body mass index (BMI) z-score, family income to poverty ratio and levels of leisure-time physical activity, respectively. p-value was calculated by the Rao–Scott Chi-squared test and t-test for categorical and continuous variables, respectively.